<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        section{
            width: 100%;
            height: 300px;
            background-color:pink;
        }
        div{
            display: inline-block;
            float: left;
            width: 50%;
            height: 100%;
            background-color: skyblue;
        }
        div:first-child{
            background-color: greenyellow;
        }
    </style>
</head>
<body>
    <section>
        <div>1</div>
        <div>2</div>
    </section>
</body>
</html>